Electronic devices such as power amplifiers, power supplies, multi-chip modules, electronic hybrid assemblies such as power amplifiers, microprocessors and passive components such as filters may contain heat sources which require cooling during normal operation. Various techniques may be used for cooling electronic devices. Traditionally, electronic devices have been cooled by natural or forced air convection which involves moving air past conduction heat sinks attached directly or indirectly to the devices.
Efforts to reduce the size of devices have focused upon increased integration of electronic components. Sophisticated thermal management techniques using liquids, which allow further abatement of device sizes, have often been employed to dissipate the heat generated by integrated electronics.
Two-phase thermosyphons have been developed to provide cooling for electronic devices. Two-phase thermosyphons typically include a cooling liquid, often a two-phase material, within a housing. The two-phase material, typically a liquid, vaporizes when sufficient heat density is applied to the liquid in the evaporator section. The vapor generated in the evaporator section moves away from the liquid towards the condenser section. In the condenser section, the vapor transforms back to liquid by rejecting heat to the ambient atmosphere. This phase-change cycle is used to spread the heat dissipated by discrete devices over a larger area, resulting in lower device temperatures compared to conventional heat sinks.
In a two-phase thermosyphon, the operating temperature of the unit is dictated by a balance between the heat input to the system and the heat rejected. Based upon the resulting temperature, the thermosyphon has a corresponding internal pressure which is dictated by the fluid properties.
A lightweight, compact design of two-phase thermosyphon typically includes a thin-shell housing with an porous structural material core that is vacuum brazed together to yield a unit with high seal integrity. At normal operating temperatures, the two-phase fluid yields a corresponding pressure that is near or below ambient conditions. Thus the unit is very structurally sound. However, in the event of extreme increases in the temperature, such as during a fire, the internal pressure will exceed the unit's structural limits causing it to burst or structurally fail in a highly unpredictable manner.
There is therefore a need for incorporating a device for pressure relief at a predetermined pressure which maintains the seal integrity of the thermosyphon for normal operation and does not increase the unit's compact size.